===== 11.8.1. Format Constraints =====
MEncoder is capable of creating VCD, SCVD and DVD format MPEG... onjunction with vcdimager or dvdauthor to create discs that will play on a standard set-top player.
T... For 30 fps material the largest allowed GOP size is 18. For 25 or 24 fps, the maximum is 15. The GOP size is set using the keyint option.
11.8.1.3. Bitra